### Answer
An "unknown-error" status in a call indicates an issue that prevented the call from completing as expected, but it doesn't specify the exact nature of the problem. It might have occurred due to various reasons not explicitly detailed. The lack of a recording suggests that the call might not have been successfully processed or completed to reach the stage where a recording would be generated and saved.
Unfortunately, without direct access to call logs or the system, I can't provide specific details about the calls with the IDs you provided (ad6a95aa-a8d1-49d9-9443-e5e4dd45dfef, 951c0ef0-43d9-4e54-9121-e6441502d44b). The call logs available in the dashboard or direct support from Vapi would offer the most accurate information and assistance for these specific cases.
For more detailed inquiries or troubleshooting, it would be best to contact Vapi support directly.